Don't take any chances...
I would leave the plumbing winterized and use the RV park's facilities along the way until you get far enough south (probably southern Colorado or northern New Mexico) before you start using the plumbing in your RV.
Unless you know for sure that the weather during your drive is going to cooperate!
I sold my house Denver house this past February and lived in my 5'ver for three months (Jan through March) in freezing temps...
Even though I had the heated water hose (which still froze up almost every night) and heat tape on my sewer lines, and ran the furnace constantly to keep the belly from freezing, I found that most of the time I had to run off of the fresh water tank for minor things and use the RV parks showers and toilets for several weeks, making sure not to fill the gray and black tanks too quickly.
Plus, my outside shower froze up and split wide open, and of course, found out after a brief thaw and had water running out of both sides of the bottom of my trailer.
And finding the same shower to replace it with was a nightmare, even though I was right in the middle of the RV mecca of Denver (at least 10 dealerships and RV parts stores within two miles of the RV park - I-70 and Ward Rd.).
Unless you need something to do once you arrive in AZ and need the repair work to keep you occupied!
I live in Yuma, AZ now and will be floating in one of the pools here most of the winter!